The present invention concerns a method of reducing the consumption of electrical energy of an electronic time piece in which a motor supplied with electrical energy supplies mechanical energy to drive a time data display unit. The invention also concerns an electronic time piece in which the method is used and comprising a motor driving a time data display unit, an oscillator used as time base, a frequency divider coupled to the oscillator, and a supply circuit coupled to the divider and delivering electrical energy to the motor.
In a time piece of the above type, the greatest part of the energy supplied by the electrical supply source, which is generally a battery, is consumed by the motor. The mean current absorbed by the latter is in fact of the order of two microamperes while the other electronic circuits of the watch (oscillator, divider, etc.) combined in an integrated circuit together consume less than 0.5 microamperes. It is therefore important to limit the motor's consumption as much as possible to increase the life of the battery or to be able to make the volume of this battery smaller, for a given life.
The motor receives driving pulses from a shaper circuit supplied with low frequency signals by a frequency divider connected to a quartz oscillator which forms the time base of the watch. In known watches the shaper circuit is adjusted so as to supply sufficient power to make the motor function in the worst conditions that may possibly occur: low battery voltage, driving of the calendar mechanism, clogging or irregularity of the gears, shocks, etc. As these bad conditions are only rarely encountered, the power supplied to the motor is most of the time far greater than that necessary for making it function reliably. There is therefore a waste of energy involved.
The object of the present invention is to avoid this waste.